According to the state of the art, and as it is generally known by those skilled in the art, most hermetic compressors applied to refrigeration systems are provided with a device disposed inside the compressor housing, and, more specifically in the suction line and/or discharge line, which purpose is, in addition to conveying refrigerant gas, to reduce the noise caused by strokes and vibrations of suction valve and compression chamber, It also aims at thermally insulating refrigerant gas.
These acoustic attenuator devices, also known as “muffler”, may have different nomenclatures when defining their installation position relative to a compression unit. For example, the terminology suction filter or suction muffler is very common when an attenuator device is disposed in the suction line so as to conduct the refrigerant gas from the strainer to the suction valve. When said attenuator device is disposed at the compression unit, nomenclatures of expansion chamber or expansion muffler types are used.
Irrespective of the installation position, said attenuator devices known from the state of the art present relatively complex configurations and are difficult to manufacture and mount mainly because they comprise small structures and require high levels of accuracy and finishing to ensure the direction of gases, acoustic muffling and in some cases thermal insulation of these gases.
More specifically, it is observed that attenuator devices known from the state of the art comprise a hollow body within which chamber and ducts are disposed to conduct gases to and from the compression unit. As can be appreciated by a person skilled in the art, this displacement of gases is generated by pulsation of the compression chamber which, consequently, generates noises, which can be attenuated according to the specificities of these chambers and ducts through which the gases pass.
A drawback of these already known devices resides in the structural aspects for assembling these chambers and inner ducts to conduct gases. More particularly, it is noted that the present state of the art comprises chambers and ducts formed by several parts and walls which are engaged with each other to obtain an extension of pathways for gas circulation inside an attenuator device. However, considering the number of inter-related parts, it is noted that there is a great number of interaction which causes gas leakage, that is, as it is known by a person skilled in the art the greater the number of parts connected therebetween the higher is the risk of leakage, thereby directly affecting the acoustic attenuation levels, mainly operation conditions of the compressor.
Furthermore, by virtue of the features of such chambers and ducts of the state-of-the-art attenuation devices, it is verified that there is a certain limitation concerning geometrical configuration of these features since in order to obtain appropriate volume and pathway to reduce noise manufacturers use configurations which, in some cases, render the process relatively more complex and expensive.
Some examples of embodiments of attenuation devices for hermetical compressors, according the state-of-the-art knowledge, are disclosed in US2005/0031461, U.S. Pat. No. 5,201,640, U.S. Pat. No. 5,971,720 and U.S. Pat. No. 6,506,028. As can be noted, these documents basically present two huge drawbacks. The first lies in the seal level between the chambers and formed ducts, mainly because the seal, in these cases, is obtained only by virtue of interference of materials wherein this seal although being useful for many applications requires very precise and well-controlled geometries, thus compromising the production lines due to the complexity of tools and manufacture and assembling costs involved to obtain a minimal level of quality to guarantee suitable seal.
The documents US2004/179955 and U.S. Pat. No. 6,149,402 provide suction muffler for compressors in which a kind of resonance chamber is applied, said resonance chambers wherein only a small part of the refrigerant in operation may flow into; the objective of such chamber is to damp the noises, but they may affect the compressor efficiency.
Finally, the documents WO02101239, WO2013086592 and US2009257892 present suction mufflers with their peculiarities, but unable to solve the current prior art problems.
Other drawback presented by the attenuator devices known in the art concerning the configuration of inner ducts, which, in order to increase the gas conduction pathway, require more intermediate parts, thus increasing the amount of seals by simple interference of material, which will then result in more complex designs and higher manufacture and mounting costs.
Another drawback found in the state-of-the-art attenuator devices stems from the fact that their configurations do not allow one to modify the length of inner ducts, especially in the case of suction duct, which length is directly related to the actuation frequency of the suction valve. Thus, with regard to the attenuator devices of the state of the art, there is only one way of altering the length of the inner ducts which can be made by using two or more parts and, consequently, more complex and expensive designs will be required.
In view of the foregoing, one may see that the attenuator devices for hermetic compressors, according to the state of the art, present some limitations and drawbacks which have a direct impact on the attenuation level of noise, mainly because their configurations are rather complex and difficult to mount.